Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932816Ab2E0BtN (ORCPT ); Sat, 26 May 2012 21:49:13 -0400 Received: from mail-pz0-f46.google.com ([209.85.210.46]:54259 "EHLO mail-pz0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932546Ab2E0BHa (ORCPT ); Sat, 26 May 2012 21:07:30 -0400 Message-Id: <20120527010426.881231735@linuxfoundation.org> User-Agent: quilt/0.60-19.1 Date: Sun, 27 May 2012 10:04:45 +0900 From: Greg KH To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: torvalds@linux-foundation.org, akpm@linux-foundation.org, alan@lxorguk.ukuu.org.uk, Thomas Gleixner , Peter Zijlstra , Deepthi Dharwar , Trinabh Gupta , Arun R Bharadwaj , Benjamin Herrenschmidt Subject: [ 22/94] powerpc: Fix broken cpu_idle_wait() implementation In-Reply-To: <20120527010332.GA11170@kroah.com> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2568 Lines: 82 3.3-stable review patch. If anyone has any objections, please let me know. ------------------ From: Thomas Gleixner commit 9cd75e13de2dcf32ecc21c7f277cff3c0ced059e upstream. commit 771dae818 (powerpc/cpuidle: Add cpu_idle_wait() to allow switching of idle routines) implemented cpu_idle_wait() for powerpc. The changelog says: "The equivalent routine for x86 is in arch/x86/kernel/process.c but the powerpc implementation is different.": Unfortunately the changelog is completely useless as it does not tell _WHY_ it is different. Aside of being different the implementation is patently wrong. The rescheduling IPI is async. That means that there is no guarantee, that the other cores have executed the IPI when cpu_idle_wait() returns. But that's the whole purpose of this function: to guarantee that no CPU uses the old idle handler anymore. Use the smp_functional_call() based implementation, which fulfils the requirements. [ This code is going to replaced by a core version to remove all the pointless copies in arch/*, but this one should go to stable ] Signed-off-by: Thomas Gleixner Acked-by: Peter Zijlstra Cc: Deepthi Dharwar Cc: Trinabh Gupta Cc: Arun R Bharadwaj Acked-by: Benjamin Herrenschmidt Link: http://lkml.kernel.org/r/20120507175651.980164748@linutronix.de Signed-off-by: Greg Kroah-Hartman --- arch/powerpc/kernel/idle.c | 14 +++++--------- 1 file changed, 5 insertions(+), 9 deletions(-) --- a/arch/powerpc/kernel/idle.c +++ b/arch/powerpc/kernel/idle.c @@ -109,6 +109,9 @@ void cpu_idle(void) } } +static void do_nothing(void *unused) +{ +} /* * cpu_idle_wait - Used to ensure that all the CPUs come out of the old @@ -119,16 +122,9 @@ void cpu_idle(void) */ void cpu_idle_wait(void) { - int cpu; smp_mb(); - - /* kick all the CPUs so that they exit out of old idle routine */ - get_online_cpus(); - for_each_online_cpu(cpu) { - if (cpu != smp_processor_id()) - smp_send_reschedule(cpu); - } - put_online_cpus(); + /* kick all the CPUs so that they exit out of pm_idle */ + smp_call_function(do_nothing, NULL, 1); } EXPORT_SYMBOL_GPL(cpu_idle_wait); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/